The present invention relates to dimmers for electric lamps, and more particularly to an improved dimmer pack suitable for rack mounted and stand alone stage, studio and architectural lighting applications and that is small in size, reliable and inexpensive to manufacture.
Luminaires for theatrical and architectural applications are provided with power by phase angle dimmers so that the lamps of the luminaires can be dimmed to operate at selected light levels. Phase angle dimmers for this purpose are well known, and typically include solid state switches such as SCRs for interconnecting an AC power source to a lamp load. AC voltage from the source is sinusoidal. A phase control circuit renders a solid state switch conductive at a point during a half cycle of the sinusoid, the point being selected to supply to the lamp a lamp operating pulse having a desired quantity of power in order to produce a desired level of light.
Dimmers are often provided in the form of modules or packs suitable for mounting in a rack along with other dimmers and, in some applications, with control modules. Known dimmer modules can include a plurality of dimmer channels in a single modular pack for controlling a plurality of lighting loads. One example of a rack mounted dimmer module of this type is disclosed in U.S. Pat. No. 4,972,125 of Cunningham and Esakoff. The dimmer module disclosed in that patent requires external control and is not self contained. Self contained dimmer packs including all of the functionality required between the mains power supply and the lighting load may be used as stand alone units as well as in racks. In a stand alone application, it would be desirable to include convenient handles integrated into the design.
One of the goals in the design of dimmer packs is to combine high power capability and the ability to provide dimming control of multiple lighting channels, while achieving a small size. A difficulty in achieving this goal is heat dissipation. Components of the dimming circuitry, including high speed solid state switching devices and inductive chokes required for EMI suppression, generate substantial heat at high power levels. Small size results in high component and power density. Resulting high temperatures can interfere with dimmer operation and can decrease component life. Adequate cooling is important, but is difficult to achieve, particularly in a small package size operating at high power levels.
Another goal in dimmer pack design is to reduce cost. A dimmer pack typically has high voltage solid state power switching circuits, often provided with heat sinks, and inductive chokes. Also included are input interconnections for power supply mains with associated overload protection and switching and outputs for connection to the controlled lighting loads. An input for control network cabling and a user interface are typically used, together with low voltage control circuitry. A major cost factor of known dimmer packs is the labor required to mount and interconnect the many required components.
Dimmer packs must withstand rough physical treatment, for example when used for traveling theatrical productions, concerts and the like. Another goal in dimmer pack design is to provide a robust, sturdy construction able to withstand substantial forces without damage.
A primary object of the present invention is to provide an improved dimmer pack. Other objects are to provided a dimmer pack that is small in size and has high power capacity with multiple channels but is efficiently cooled; to provide a dimmer pack that that is easy and quick to assemble with low labor cost; to provide a dimmer pack that is sturdy and rugged; to provide a dimmer pack that includes convenient and strong handles integrated into the pack; and to provide a dimmer pack overcoming disadvantages of known dimmer modules and packs.
In brief, in accordance with the invention there is provided a dimmer pack for electrical lighting loads including a housing having front and rear walls spaced apart in a longitudinal direction, a bottom wall, a top wall and opposed side walls spaced apart in a lateral direction. A printed circuit main board within the housing overlies the bottom wall and is spaced from the top wall. A printed circuit second board in the housing is adjacent to the main board. The second board extends laterally between the side walls and extends vertically between the main board and the top wall and baffles air flow over the main board between the front and back walls. Cooling air inlet vents are in the housing adjacent the front wall and cooling air outlet vents are in the housing adjacent the rear wall. A high voltage switching circuit assembly and a choke are mounted on the main board at one side of the second board. An air passage opening in the second board defines a cooling air path through the second board between the inlet and outlet vents, the air passage opening being aligned with the switching circuit assembly and choke. A fan supported in the housing moves air along the cooling air path.
In brief, in accordance with another aspect of the invention, there is provided a dimmer pack for electrical lighting loads including a housing and a printed circuit board in the housing. A high voltage switching module includes a heat sink. The heat sink includes a planar base portion having first and second opposed surfaces. A plurality of cooling fins extend from the first surface. A solid state high voltage switching circuit is attached to the second surface. A plurality of first electrical connectors connected to the switching circuit project away from the second surface. A plurality of second connectors are mounted on the circuit board. The second connectors are releasably mated with the first connectors for supporting the switching module on the circuit board and for making electrical connections between the circuit board and the switching circuit.
In brief, in accordance with another aspect of the invention, there is provided a circuit breaker mounting assembly for an electrical device including a housing having a panel. The panel has opposed parallel flanges. A circuit breaker has front, top and bottom walls with recesses in the top and bottom walls. The circuit breaker is mounted adjacent the panel with the front wall against the panel and the top and bottom walls interfacing with the flanges. Tangs on the flanges are received in the recesses for locking the circuit breaker onto the panel.
In brief, in accordance with another aspect of the invention, there is provided a rack mountable electrical unit including a housing having front and side walls defining front housing corners and an integral bracket and handle member at each of the front housing corners. Each of the members includes a planar mounting portion attached to the housing, a mounting bracket projecting laterally from the housing beyond one of the side walls, and a handle spaced from and located in front of the bracket, the handle projecting laterally from the housing beyond one of the side walls.